Pressure relief valve with bi-directional seat

ABSTRACT

A pressure relief valve includes a valve body including a monitored pressure inlet leading to a monitored pressure region, a piston having a shear seal bore and a surface facing the monitored pressure region, a vent passage and a the shear seal assembly comprising a seal plate having a sealing surface thereon, and the shear seal assembly includes a sealing surface facing the seal plate and having a first annular area, and a first surface having an annular surface area at least twice as large as the first area of the sealing surface, the first surface facing away from the first area, and a biasing seal in contact with the first surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/908,317, filed Jun. 22, 2020, which claims benefit of U.S.provisional patent application Ser. No. 62/867,691, filed Jun. 27, 2019,which is herein incorporated by reference.

BACKGROUND

Pneumatically and hydraulically operated equipment and control devicesoften incorporate, and are commonly interconnected to one another using,valves. Among these valves are relief valves, wherein a monitored fluidline is connected to an inlet of the relief valve, and the relief valveselectively opens to allow pressure in the monitored fluid line to ventfrom the monitored fluid line therethrough, through a relief valve ventopening connecting the relief valve to a vent, such as the local ambientpressure or a vent line. As a result, an overpressure condition in themonitored fluid line can be relieved. In these relief valve constructs,the relief valve commonly is connected to a spring housing, whichprovides a desired closing force against the fluid at pressure in themonitored fluid line to maintain the relief valve in the closed positionwhen normal operating pressure is present in the monitored fluid lineand thus preventing fluid flow form the monitored fluid line to thevent, and which force is insufficient to maintain the relief valve inthe closed position once an undesirably high pressure is reached in themonitored fluid line and thus the relief valve opens to allow fluid inthe monitored fluid line to flow to the vent. One such relief valveincludes a piston having a shear seal element therein, the face of whichfaces a seal plate having a sealing face and an opening therethrough influid communication with the vent and commonly centered with respect tothe sealing face thereof. A compressible element is present between theshear seal element and a bore in the piston within which the shear sealelement is received and maintained. The compressible element is presentto maintain the surface of the sealing face of the shear seal elementagainst the sealing surface of the seal plate, the two sealing elementstogether forming a seal when in contact with one another and biasedtogether, with the face of the shear seal element surrounding theopening in the sealing surface of the shear seal element. When thepressure of the fluid at the valve inlet, which is received through theinlet from the monitored fluid line and which fluid is in contact withthe piston, creates a force on the piston greater than the force of themain spring holding the piston in place, the piston moves linearly tolinearly move the shear seal element, and thus the sealing face thereof,past the opening in the seal plate, thereby allowing fluid to flow fromthe monitored fluid line and therethrough to vent. Thus, the fluid andpressure in the monitored fluid line can be relieved to the vent, andwhen the desired pressure is re-achieved in the monitored fluid line,the pressure of the fluid from the monitored fluid line against thepiston is insufficient to maintain the piston in the retracted, ventopen position, and the piston moves to again position the shear sealelement over the opening in the seal plate.

Relief valves are constructed with a uni-directional seat bias, becausethe inlet pressure to the valve is used to bias the annular sealing faceof the shear seal element against the shear plate to assist in thesealing off of the inlet pressure from the vent pressure during periodswhen normal pressure is present in the monitored fluid line, i.e., tomaintain the sealing face of the shear seal element against the sealingsurface of the seal plate in facing, sealing, contact. One issueencountered in this relief valve construct is the undesirable liftingoff of the shear seal element from the seal plate occurring when thepiston is in the valve closed position, which occurs as a result of anoverpressure condition in the vent line causing the shear seal elementto retract inwardly of the shear seal element bore in the piston. Whenthis occurs, the sealing integrity of the relief valve is lost, and insome cases, the shear seal element can become cocked in the bore in aretracted position from the seal plate, and the shear seal elementbecomes resultantly seized in the piston, resulting in failure of therelief valve. One cause of such an overpressure condition is theconnection of multiple valve outlets to the vent line, such that thevent line pressure can exceed the inlet pressure at the inlet to arelief valve connected thereto.

One attempt to overcome this issue is embodied in U.S. Pat. No.6,651,696, wherein the shear seal element includes a through passagetherein and thus the pressure is equal on either side of the shear sealelement, even when the vent pressure is abnormally high. This canprevent the shear seal element from lifting off (i.e., backing awayfrom), the seal plate, but the force of the sealing face of the shearseal element bearing against the sealing surface of the seal plate isinsufficient to provide a reliable seal at that interface and the fluidin the monitored fluid line can leak past the sealing face of the shearseal element and the facing sealing surface of the seal plate, and thusto the vent.

Additionally, relief valves are commonly tested after their manufactureor refurbishment, to determine the inlet pressure at which the vent linewill be exposed to the inlet pressure through the valve for a givenspring force setting, commonly known as when the valve or seal of thevalve seat “cracks” open. This testing can be performed by connectingthe valve inlet to a variable pressure fluid source, raising thepressure at the valve inlet over a predetermined time period, anddetermining the occurrence pressure at which the seal of the valvecracks open, by the occurrence of fluid flowing through the valve ventpassage or a change in the smooth rise of pressure being increased inthe valve inlet, i.e., the monitored fluid line inlet. However, once thevalve is installed in a fluid circuit, it becomes difficult orimpossible to monitor the opening pressure of the relief valve in situ.

SUMMARY

Provided herein are relief valves wherein an overpressure condition inthe vent bore has limited to no impact on valve performance, wherein abi-directional seal is engaged between the shear seal element and aportion of the shear seal element bore. The shear seal element isreceived in a cross bore in the seal piston, which piston is biasedinwardly of the valve body by a user settable bias spring, and the shearseal element includes an annular seal face having a first annular area,and an annular pressure leveraging face having an area at least twicethat of the first annular area. Additionally, a seal element is providedsurrounding the body of the shear seal element, in one aspect, incontact with the annular pressure-leveraging face of the shear sealelement. The sealing element extends between the body of the shear sealelement and the inner circumferential surface of the cross bore, to sealthe inlet side pressure of the relief valve from the vent side pressurethereof.

Additionally, a relief valve having a mechanism to enable checking ofthe valve opening pressure in-situ, under valve operating ambientconditions, is provided. Here, a check valve is provided between thevalve inlet and the piston of the valve, and is set to close off theinlet when the pressure in the interior volume of the valve is greaterthan the inlet pressure. A pumping port is provided through the body ofthe valve and it extends from the exterior of the valve into theinterior volume thereof, on the side of the check valve opposite that ofthe inlet. A plug is normally maintained in this pumping port. However,to check the opening pressure of the valve, the pumping port plug isremoved, and a variable fluid source is attachable to the pumping portto elevate the pressure in the inner volume of the valve to a valueexceeding that of the check valve closing pressure vis a vis the inletpressure, and to continue to raise that pressure to a pressuresufficient to cause movement of the piston to “crack” open the seal ofthe valve. The pressure being supplied into the valve interior volume ismonitored to determine the pressure at which the valve opens in situ,and may be used to adjust the spring force on the piston to change theopening or “cracking” pressure of the valve, after which the openingpressure may be again checked by pumping fluid inwardly through thepumping port, which can be repeated until a desired opening pressure isachieved and the relief valve is thus properly calibrated.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1 is an isometric view of a relief valve;

FIG. 2 is a sectional view of the relief valve of FIG. 1 , showing therelief valve is the closed position;

FIG. 3 is an enlarged sectional view of a the shear seal elements of thevalve of FIG. 1 ;

FIG. 4 is an enlarged sectional view of a the shear seal elements of thevalve of FIG. 3 ;

FIG. 5 is an enlarged sectional view of a the shear seal elements of thevalve of FIG. 1 in the fully open condition;

FIG. 6 is an enlarged sectional view of a the shear seal elements of thevalve of FIG. 1 as the valve is transitioning from a fully closed to anopen condition;

FIG. 7 is an enlarged view of the seal gland of the shear seal elementsof the valve of FIG. 1 , showing the biasing seal therein during a highpressure condition in the line to which the valve is connected, i.e.,the monitored fluid line;

FIG. 8 is an enlarged view of the seal gland of the shear seal elementsof the valve of FIG. 1 , showing the biasing seal therein during a highpressure condition in the vent to which the relief valve vents anoverpressure condition in the monitored fluid line;

FIG. 9 is an enlarged sectional view of a bi-directional shear sealuseful with an alternative relief valve construct;

FIG. 10 is an enlarged sectional view of a portion of the valve of FIG.1 , showing elements of the in situ pressure checking elements thereof;and

FIG. 11 is an enlarged sectional view of a portion of the valve of FIG.1 , showing a pump fluidly connected to the internal bore thereof.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2 , the exterior of a relief valve 10 is shown,wherein the relief valve 10 includes a body 12, connected to which are aspring cap 14 received within, and connected to, a spring bore 22 (FIG.2 ) of the body 12, such as by being threaded thereinto, a ventconnector 16 received and secured in, a vent connector recess 24 (FIG. 2) extending inwardly of the body 12, an inlet connector 18 secured overthe base 26 of the body 12, and a pumping port plug 20 releasablysecured in an auxiliary pumping port 28 (FIG. 2 ) extending through thevalve body 12 from the inner volume 30 to the outer surface 32 thereof.A spring 34 is provided within a volume formed of the spring bore 22 andthe generally hollow interior of the spring cap 14, and a spring plate36 is provided at the base of the spring bore 22. Spring cap 22generally includes a cover portion 37 generally formed as a generallycircular disk from which extends an annular sleeve 38 terminating at adistal annular end wall 40. The outer surface of the annular sleeve 38includes a continuous thread or threads 42 running on the outer surfacethereof in the direction from the distal annular end wall 40 andterminating before reaching the end of the spring cap 22, and aplurality of vents 44 in the form of openings extending through theannular sleeve 38 are disposed adjacent to the cover portion 36 end ofthe spring cap 14. The inner surface of the spring bore 22 is likewisethreaded with inner threads 46 which mate with threads 42 on the outercircumferential surface of the annular sleeve 38. The spring plate 36 atthe base of the spring bore is biased in the direction of the base ofthe spring bore 22 by the spring 34. The force of the spring 34 againstthe upper surface of the spring plate 36 is adjustable and is set byadjusting the compression of the spring 34, which here is configured asa coil spring. This adjustment is made by rotating the spring cap 14with respect to the body 12 of the valve 10, such that the distancebetween the inner surface of the cover portion 37 and the base of thespring bore 22 is changed by threading the spring cap 22 inwardly oroutwardly of the spring bore 22. To readily achieve this movement, acontoured opening 48 extends through the cover portion 36 of the springcap 14, and here it is configured as the female side of a hexconnection, wherein a hex wrench having six equal sides may be insertedthereinto and pushed or pulled to rotate the spring cap 14 with respectto the body 12 Additionally, a lock nut 50, having a generally circularinner opening having threads which mate with the threads 42 on the outersurface of the spring cap 14 is provided over the annular sleeve andthreaded thereto. Once the desired location of the spring cap 14 isachieved with respect to body 12 and the base of the spring bore 22,i.e., the proper spring force or compression has been set, the nut 50 isrotated to bring it to bear against the upper circumferential surface 52of the body, to lock the spring cap 14 location with respect to the body12. Additionally, a plurality of secondary vent holes 54 (two shown)extend through the wall of the spring cap 22.

Vent connector 16 extends inwardly of vent connector recess 24 and issecured therein such as by a plurality of fasteners extending throughthe vent connector 16 and into corresponding threaded holes in the body12, by being threaded therein, or other mechanism. A seal plate opening56, into which a seal plate adaptor 58 is received, extends inwardly ofthe body from generally the center of the vent connector recess 24 andinto the inner volume 30 of the body 12. The inner volume 30 of the body12 further includes a central bore region, including a first bore 60having a first opening area, a second bore 62 having a second openingarea, and a third bore 64 having a third opening area. In this aspect, apiston 66, having a first portion 68 and a second portion 70,reciprocally extends within the second and third bores 64, 66, such thatthe first portion 68 is located within, and is reciprocally movablewithin, a portion of the second bore 62, and the second portion 70extends within a portion of the second bore 62 and in the third bore 64,and inwardly of the spring bore 22 at one end thereof. The first bore 60opening area (i.e., cross sectional area) here is larger in crosssection than the second bore 62 opening area, which in turn is larger incross section than the third bore 64 opening area. Here, the bores 62,62, 64 have a circular, within machining tolerance, circumference,wherein the diameter of the first bore 60 is greater than the diameterof the second bore 62 with is larger in diameter of the third bore 64.Resultantly, a first annular ledge 72 is present and extends between thefirst bore 60 and the second bore 62 inwardly of the body 12, and asecond annular ledge 74 (FIG. 3 ) is present and extends between thesecond bore 62 and the third bore 64 inwardly of the body 12 and islocated between the first annular ledge 72 and the spring bore 22.

FIG. 3 depicts the basic interactive structure of the piston 66, sealplate adaptor 58 and a shear seal element 76 received within a shearseal element bore 78 in the piston 66. Piston 66, includes the firstportion 68 from which second portion 70 extends, each of which has acircular, within machining tolerances, circumference or cross section,wherein the circumference of the first portion 68 is one to 3thousandths of an inch less than that of the second bore 62, and whereinthe circumference of the second portion 70 is one to 3 thousandths of aninch less than that of the third bore 64, allowing sliding motion of thefirst and second portions 68, 70 of the piston 66 within the second andthird bores 62, 64 respectively. First sealing guide shims 61 a, b arereceived in an annular groove 63 extending around the second portion 70,and help center the second portion 70 in the third bore, and a secondsealing guide shim 65 is received in a groove 69 extending inwardly ofthe circumference of the first portion 68 of the piston 66, and helpscenter the second portion 68 in the second bore 62. Sealing shims 61 a,b and 65 also seal the annular gap between the outer surfaces of thefirst and second portions 68, 70 of the piston 66 and the inner walls ofthe second and third bores 62, 64, to seal off the open area (springbore 22) of the spring cap 14, which is at the ambient pressuresurrounding the relief valve 10, from the central bore region of thebody 10, i.e., the volume of the second bore 62 in the region of thesecond bore 62 between the second guide shim 65 and the first annularledge 72 and the volume of the first bore 60. Additionally piston 66includes a flatted portion 82, extending across the outer circumferencethereof from the end 84 of the piston 66 distal of the second portion 70to a limit ledge 86 extending generally perpendicularly to flattedportion 82. The distance between the closest location of the seal plateadaptor to the second annular ledge 74, less the distance between thelimit ledge 86 and an annular wall 90 at the change in piston 66circumference between the first and second portions thereof, defines themaximum stroke distance of the piston 66 within the second and thirdbores 62, 64.

Shear seal element bore 78 of the piston 66 includes a major bore 92opening at the flatted portion 82, and a minor bore 94 extending alongthe centerline of the major bore further inwardly of the piston 66therefrom, and connected by an annular bore ledge 96. Shear seal element76 includes a corresponding major portion 100 received within the majorbore 92, a minor portion 102 received within the minor bore 94, and anannular shear seal element ledge 104 interconnecting the major and minorportions 100, 102. Shear seal element 78 further includes a minor sideface 106, a major side end 108 having an annular seal face 110surrounding a recess 112, and a central shear seal element bore 114extending from recess 112 thorough the minor side face 106.

Body 12 further includes the seal plate opening 56, into which the sealplate adaptor 58 extends from the base of the vent connector recess 24through the wall of the body 12 and to the second bore 68. Seal plateopening 56 includes a major seal plate opening bore 116 and a minor sealplate opening bore 118, and an annular seal plate adaptor bore ledge 120interconnecting the inner circumferential surfaces of the major sealplate opening bore 116 and minor seal plate opening bore 118. Seal plateadaptor 58 likewise includes a major seal plate adaptor portion 122received in the major seal plate opening bore 116, a minor seal plateadaptor portion 124 received in the minor seal plate opening bore 118,and an annular seal plate adaptor ledge 126 connecting the surface ofthe major seal plate adaptor portion 122 to the surface of the minorseal plate adaptor portion 124. Here, the major seal plate opening bore116 and minor seal plate opening bore 118 are, within machiningtolerances, circular in section, and the major seal plate adaptorportion 122 and the minor seal plate adaptor portion 124 are likewisehere, within machining tolerances, circular in section, having acircumference 1 to 3 thousandths of an inch less than that of the majorseal plate opening bore 116 and minor seal plate opening bore 118 toallow the minor seal plate adaptor portion 124 to be slid into the sealplate opening 56 until the annular seal plate adaptor ledge 126 abutsthe annular seal plate adaptor bore ledge 120, thus positioning thecircular end face of the seal plate adaptor 58 forming the seal platesurface 130 thereof inwardly of the second bore, in a spaced facingrelationship with the flatted portion 86 of the piston 66, such that thelimit ledge 86 of the piston overlies, and is limited in motion in thedirection away from the spring bore 22, by the portion of the minor sealadaptor portion 124 extending inwardly of the second bore 68, and theannular seal face 110 of the shear seal element 76 faces and contactsthe seal plate surface 130. A seal groove 136 extends inwardly of thecircumferential surface of the minor seal plate adaptor portion 124, anda seal ring 134, and backing rings 132 on opposed sides thereof, arereceived in the seal groove 136 to provide a seal across the smallannular gap between the outer circumferential surface of the minor sealplate adaptor portion 124 and the inner circumferential surface of theminor seal plate opening bore 118. Seal plate adaptor 58 furtherincludes a rear wall 138, facing away from seal plate surface 130 and onan opposed end surface of the seal plate adaptor 58 therefrom, and athrough vent bore 140 extends through the seal plate adaptor 58 from andthrough rear wall 138 and to and through seal plate surface 130. Ventconnector 16 includes a vent opening 142 therein which fluidlycommunicates with the through bore 140 of the seal plate adaptor 58which in turn, in the relief valve closed position shown in FIG. 3 ,communicates with the recess 112 and central shear seal element bore 114to communicate ambient pressure around the valve body 12, or a vent linepressure where a vent line (not shown) is connected to the vent opening142, to a volume between base wall 158 (FIG. 4 ) of the minor bore 94 ofthe shear seal element bore 78 and the minor portion 102 of the shearseal element 76. The vent connector 16 contacting the rear wall 138 ofthe seal plate adaptor 58 prevents backing of the seal plate adaptor 58from the seal plate opening 56 to maintain the proper position of theseal plate surface 130 within the second bore 62 of the valve body 12.

Referring to FIG. 4 , the relative sizes of the regions of the shearseal element bore 78 and the annular seal face 110 are shown anddescribed. In this aspect of the relief valve 10, the annular seal face110 has a radial width 144, defining a first seal face surface area.Annular bore ledge 96 has a bore ledge radial width 146 defining a boreledge area, and annular shear seal element ledge 104 has a radial width148 defining an annular shear seal element ledge area. The annular boreledge 96 is separated from the annular shear seal element ledge 104 by agap 152, in which a circumferential biasing seal 150, such as an O-ring,is disposed and contacts and biases apart the annular bore ledge 96 andthe annular shear seal element ledge 104 across the gap 152. When thepressure in the second bore 62 is greater than that in the vent bore140, the biasing seal 150 surrounds and sealingly contacts the outersurface of the minor portion 102 of the shear seal element 76 and canbecome spaced from, i.e., can be lifted off of, the surrounding surfaceof the major bore 92 in the gap 152, and can lift off of the annularshear seal ledge 104. The outer diameter of the annular seal face 110 isgreater than the inner diameter of the vent bore 140, ensuring that aportion of the annular seal face 110 can surround the opening of thevent bore 140 into the second bore 62. To ensure sealing of theinterface of the seal plate surface 130 and the annular seal face 110,the radial width 144 the annular seal face is chosen such that theannular shear seal ledge area of the annular seal shear ledge 104 isgreater than the resulting first seal face surface area of the annularseal face 110, such that the second bore pressure 62 on the annular sealledge 104 forms a pressing force to push annular seal face 110 towardthe seal plate surface 130 greater than that tending to push the shearseal element 76 away from the seal plate surface 130. Likewise, theradial width 146 of the annular bore ledge 96 is chosen such that theresulting second seal face surface area is greater than the surface areaof the annular seal face 110.

The minor side face 106 of the shear seal element 76 is an annularsurface having a radial width 156 establishing a first vent pressurebiasing area on the shear seal element. The presence of the biasing seal150 maintains the vent pressure on the minor side face 106 whilepreventing the second bore 62 pressure from reaching the minor side face106. The base of the shear element bore 78 is an annular wall 158 havinga radial width 154 greater than that minor side face establishing asecond vent pressure biasing area. A small annular area of the annularseal face 110 directly adjacent to the recess 112 is, in the reliefvalve fully closed position of FIGS. 1 to 4 , likewise exposed to ventpressure and thus forms a third vent pressure biasing area. As thesecond and third vent pressure biasing areas are, in sum, greater thanthat of the first vent pressure biasing area on the minor side face 106,vent pressure tends to push the shear seal element 76 away from theshear plate adaptor 58, or in other words, tends to lift the sealsurface 110 off of the seal plate surface 130. In contrast, themonitored fluid line pressure present in the second bore 62 communicatesthrough a first annular passage 174 between the major portion 100 of theshear seal element 76 and the major bore 92 to maintain monitored fluidline pressure on the annular shear seal element ledge 104, to push theannular seal face 110 into engagement with the shear plate 130 surface.By ensuring the area of the annular shear seal element ledge 104 is atleast twice that of the annular seal face 110, a safety margin is builtinto the seal arrangement for the relief valve to maintain the shearseal element 76 against the seal plate adaptor 58, even when the ventpressure rises to that of, or slightly more than, the pressure in secondbore 62 which is a monitored or protected line pressure.

A seal gland 176 is formed in the gap 152 bounded by the annular boreledge 96, the annular shear seal element ledge 104, and portions of theouter circumferential surface of the minor portion 102 of the shear sealelement 76 and of the major bore 92 of the shear seal element bore 78extending therebetween. The biasing seal 150 here is an O-ringcircumscribing the shear seal element 76 within the seal gland 176. Inits non-compressed state, the biasing seal 150 has a nominally, withinmanufacturing tolerance, circular cross section, and the seal gland 176has a generally rectangular cross section, having a width 178 which isless than the diameter of the biasing seal 150 in its free, unbiasedstate and a radial depth which is likewise less than the diameter of thebiasing seal 150 in its free and unbiased state. For example, the width178 of the seal gland 176 is approximately 95% the diameter of thebiasing seal 150 in the free, unconstrained, state of the biasing seal150, and the depth 180 of the seal gland 176 is approximately 83% thediameter of the biasing seal 150 in the free, unconstrained, state ofthe biasing seal 150. Thus, when the shear seal element 76 is assembledinto the shear seal element bore 78 of the piston 66, and the shear sealelement 78 contacts the seal plate adaptor 58, the biasing seal 150 iscompressed into an ovoid shape as shown in FIGS. 2 to 6 , such that thebiasing seal 150 is compressed into four flatted regions at the contacttherewith with each of the annular bore ledge 96, the annular shear sealelement ledge 104, and portions of the outer circumferential surface ofthe minor portion 102 of the shear seal element 76 and of the major bore92 of the shear seal element 76, and curved outer portions betweenadjacent flatted areas thereof. As shown in FIG. 4 , the biasing seal150 separates a monitored fluid line pressure annular area 182 when thevalve is assembled and not under pressure at the inlet or vent initiallybounded by surfaces of the biasing seal 150 extending between annularbore ledge 96 and the annular wall of the major bore 92, and a ventpressure annular area 184 initially bounded by surfaces of the biasingseal 150 extending between the major bore 92 and the annular shear sealelement ledge 104 of the shear seal element 76.

During use, the pressure in the monitored fluid line communicated to thesecond bore 62 through the first bore 60 and the inlet 170 in the inletconnector 18 may experience a pressure increase sufficient to cause thepiston 66 to move in the direction of spring bore 22, causing theannular seal face 110 to likewise move in the direction of spring bore22. The spring plate 36 includes a generally planar lower face 162,having a central conical detent 160 extending thereinto. The secondportion 70 of the piston 66 includes, at the terminal end thereofopposed to the first portion 68 of the piston 66, a hemispherical endportion 166 sized to be received within and engage the internal surfaceof the conical detent 160, which resultantly causes circumferential linecontact between the hemispherical surface of the end portion 166 and thesurface of the conical portion 160. This allows the spring plate 36 andthe lower face 162 thereof, if moved away from the base wall 168 of thespring bore 22, to tilt or move into a non-parallel relationship withthe base wall 168 which occurs because the spring may load only againsta portion of the spring plate 36. As this movement of the piston 66continues, the maximum movement of the piston from the position thereofin FIGS. 1 to 4 is shown in FIG. 5 , whereby the annular wall 90 of thepiston abuts against, and is limited from further movement in thedirection away from first bore 60 by contact with, the second annularledge 74.

The position and biasing functionality of the circumferential biasingseal of FIGS. 2 to 6 during valve use and operation is shown in FIGS. 7and 8 . Here, in FIG. 7 , the vent pressure is at a low ambientpressure, for example atmospheric air pressure where the vent is open tothe earth's atmosphere, or the water pressure at the depth of the valveinstallation location, and the valve 10 bore area, including the firstand second bores 60, 62, is charged with a monitored fluid line pressuregreater than the pressure of the vent. In this condition, the pressurein second bore 62 communicates through a gap 172 between the shear sealelement 76 and the seal plate surface 130 (FIG. 4 ), thence along orthrough the annular passage 174 between the major portion 100 of theshear seal element 76 and the major bore 92 and thence into themonitored fluid line annular pressure area 182 of the seal gland 176.This high pressure compresses the biasing seal 150 radially inwardlysuch that the biasing seal 150 no longer contacts the major bore 92. Themonitored fluid line pressure is thus present between the biasing seal150 and the major bore 92 of the shear seal element bore 78. As themonitored fluid line pressure is originally present at monitored fluidline pressure annular area 182 (FIG. 4 ), it is believed that theincrease in monitored fluid line pressure further compresses the biasingseal 150 into the shape of the seal gland 174 leaving an outercircumferential gap 186 between the surface of the biasing seal 150facing away from the minor portion 102 of the shear seal element 76 andthe inner surface of the major bore 92. The pressure in this outercircumferential gap 186 compresses the biasing seal such that the forceexerted by the biasing seal 150 against the annular bore ledge 96 andopposed annular shear seal element ledge 104 is increased toapproximately the pressure value of the monitored fluid line pressure,such that the compressed biasing seal biases against an area at leasttwice the annular area of the annular seal face 110 at or nearly at theincreased vent pressure to maintain the seal between seal face 110 andthe seal plate surface 130.

In contrast, as shown in FIG. 8 , vent pressure is communicated throughthe seal element bore 114, between the region between the base of theminor bare and the minor side face 106 of the shear seal element 76,through a second annular passage 190 and thence to the vent pressureannular area 184. When an overpressure condition occurs in the vent andthis pressure sufficiently exceeds the pressure in the monitored fluidline, this higher pressure pushes the biasing seal outwardly and extendsthe vent pressure annular area 184 and is believed to flatten orcompress the biasing seal 150 against the inner circumferential surfaceof the major bore 92, and the vent pressure compressing the biasing sealcauses the pressure or force applied by the biasing seal 150 against theannular shear seal element ledge 104 to be approximately that of thevent pressure, and the area of the annular shear seal element ledge 104exposed to the vent pressure is greater than the area of the seal face110 contacting the seal plate surface 130. By sizing the annular shearseal element ledge 104 to have an area at least twice that of theannular seal face 110, maintenance of a seal between seal face 110 andthe seal plate surface 130 is maintained because the area of the annularshear seal element ledge 104 is at least twice as large as the area ofthe annular seal face 110 facing the seal plate surface 130, and anexposed portion of the annular shear seal element ledge 104 is alsoexposed to the higher vent pressure as well as the increased force ofthe biasing seal 150 which is now at, or near, the increased ventpressure likewise pushing against the shear seal element ledge 104 inthe direction of the seal plate surface 130.

As the piston begins moving from the valve fully closed position of FIG.4 toward the fully opened position of FIG. 5 , when the initial movementdistance exceeds the radial width 144 of the annular seal face 110, atthe point in time the lowermost portion of the major portion 100 movespast the lowermost portion of the bore 140 of the seal plate adaptor 58,also known as when the seal “cracks”, the second bore 62 will becomeexposed to the vent bore 142 through the bore 140 of the seal plateadaptor 58, and fluid will be vented from the second bore and thus froma monitored fluid line fluidly connected to the valve through the inletbore 170 in the inlet connector 18 to relieve the pressure in themonitored fluid line as shown by arrow F in FIG. 6 .

FIG. 9 is a partial sectional view of an additional relief valveconstruct, showing a bi-directional sealing element therein. Here, incontrast to the relief valve 10 of FIGS. 1 to 6 wherein the ventpressure is located at a single port of the valve, here vent pressureopenings are located at opposed sides of the valve and aligned with oneanother over the width of the valve body. The structure of the valve andthe components thereof having the bi-directional sealing element arestructurally the same as those having the uni-directional sealingelement, except as shown in FIG. 9 .

Here, to form the bi-directional relief valve 200, valve 10 of FIGS. 1to 6 is modified such that two shear seal assemblies, here first andsecond shear seal assemblies 202, 204, and two, here first and second,seal plate adaptors 206, 208 are used, and the piston hereof hasgenerally the same construct as piston 66, except here it is a dualflatted piston 210 which is modified to include opposed flatted portions82 a, b and limit ledges 84 a, b. First shear seal assembly 202 isconfigured substantially the same as shear seal assembly 76 of valve 10,and includes the annular seal face 110 and annular shear seal elementledge 104 having the same relative dimensions as those in valve 10, andthe biasing seal 150 having the same relative dimensions to the annularseal face 110 and annular shear seal element ledge 104 as it does inrelief valve 10. In contrast to the relief valve 10, bi-directionalrelief valve 200 includes a second shear assembly 204 having a secondannular seal face 110 a and second annular shear seal element ledge 104a, and a through bore 212 having an inner surface 214 having acircumference or diameter slightly greater than the outer circumferenceor diameter of the minor portion 102 of the first shear seal assembly202. Dual flatted piston 210 also includes, in contrast to piston 66, athrough shear seal bore 220 having an inner circumferential surface 222having a diameter or circumference. The space between the annular shearseal element ledges 104, 104 a, and the portions of the innercircumferential surface 222 of the shear seal bore 220 and of the minorportion 102 of the first shear seal assembly 202 extending between theannular shear seal element ledges 104, 104 a forms a bi-directional sealgland 218. Additionally, here biasing seal 150 is present in thebi-directional seal gland, and where the valve is not under pressure,i.e., not installed, the biasing seal 150 forms four flatted portionscontact the four surfaces defining the bi-directional seal gland 218,similarly to the biasing seal 150 in FIGS. 2 to 6 .

The bi-directional seal of the valve 200 operates substantially the sameway as that of valve 10, except here two vent bores 142 a, 142 b arecollinearly provided on opposed sides of the valve body, and when thevalve 200 is in the fully closed position, vent bore 142 a is alignedwith recess 112 within the circumference of annular seal face 110, andvent bore 142 b is aligned with through bore 212. In this condition,pressure in the monitored fluid line is present in the second bore 62,and communicates in the small clearance between the innercircumferential surface 222 of the shear seal bore 220 of the dualflatted piston 210 and the facing outer circumferential surfaces of themajor portion 100 of the first shear seal 202 assembly and the outercircumferential surface of the second shear seal assembly 204, to loadthe biasing seal 150 as shown in FIG. 7 when a high pressure is presentin the monitored fluid line. When an overpressure condition is presentin the vent bores 142 a, b, through the small clearance between theminor portion 102 of the first shear seal assembly 202 and the innersurface 214 of the second shear seal assembly, to load the biasing sealsuch that the biasing seal is spaced from the outer circumferentialsurface of the minor portion 102 of the first shear seal assembly 202and further biased against as the inner circumferential surface 222 ofthe shear seal bore 220, similarly to the pressure biased position ofthe biasing seal as shown in FIG. 8 . Again the surface area of theannular surfaces of each of the annular shear seal element ledges 104,104 a is at least twice that of the annular surface area of each of theannular seal faces 110, 110 a, and the loading effect resulting from theannular seal element ledge being at least twice as large in area as theannular seal face 110 of the aspect hereon shown and described withrespect to FIGS. 2 to 8 is also achieved here.

Referring again to FIGS. 1 and 2 , relief valve 10 further includes theauxiliary pumping port 28 extending from, and fluidly connecting, theexterior of the relief valve body 12 to the second bore 62 within therelief valve body 12, within which a removable pumping port plug 20 islocatable and is configured to seal off fluid flow through the auxiliarypumping port 28, and a check valve assembly 304 received in first bore60 and secured therein between first annular ledge 72 and the facingsurface of the inlet connector 18 secured over the base 26 of the body12. First bore 60 and an inlet bore 170 extending through the inletconnector 18 are aligned for fluid communication therebetween. Inletconnector 18 is secured over the base 26 of the body by, for examplethreaded fasteners, a clamp, or other attachment mechanism. As will bedescribed further herein, the cracking pressure of the valve, or theshear seal therein, may be tested using the auxiliary pumping port 28 toincrease the pressure in the second bore 62 independently of thepressure in the vent opening 142 in the vent connector 16 and thepressure in the monitored fluid line fluidly communicated to the secondbore 62 through the inlet bore 170.

Referring to FIGS. 11 and 12 , the check valve assembly 304 andauxiliary pumping port region of the valve are shown enlarged and insection. In FIG. 11 the closure element 308 of the check valve assemblyis in the closed position as also shown in FIG. 2 , and in FIG. 10 theclosure element 308 of the check valve assembly 304 has been moved to avalve open condition in contrast to the check valve closed position ofFIGS. 2 and 11 . Here, check valve assembly 304 is received within thefirst bore 60 of the valve body 12, and held between the first annularledge 72 at the interface of the first and second bores 60, 62, and thebody facing surface of the inlet connector 18 extending across thecircumference of the opening of the first bore 60 at base 26 of the body12. Check valve assembly 304 includes a first body 312 in the form of acup, a second body 314 having a male threaded portion 316 extendinginwardly of the cup shaped recess of the first body 314, a check valvespring 318, the closure element 308, a backing ring 320 and aconformable seal ring 322 having an inwardly facing frustoconicalsealing surface. First body portion 312 here includes a base portion 324having a central through opening 326 therethrough, the upper portion ofwhich is configured as a seat 356, an annular wall 334 extendingtherefrom further inwardly of the first bore 60, and together with thebase portion 324 creating a cup shaped recess having an innercircumferential wall 330 having threads, mating with those on malethreaded portion 316 of the second body 314. The cup shaped recessincludes, at the base thereof, an annular backing ring ledge 335surrounding a first opening area, and a conformable ring ledge 336surrounding a second opening area having a smaller opening area than thefirst opening area. The second body 314 includes a first annular portion338 from which the male threaded portion 316 in the form of an annularwall extends to end at an annular bias wall 340. Closure element 308incudes a spring recess 342 formed of an annular closure element wall344 and an annular closure element spring ledge 346, and a cage 348extending therefrom and including a plurality of flow openings 350extending through a side wall thereof and terminating in a conicalportion 352 having a frustoconical sealing or seating surface 354thereon, which follows a different conical contour than that of theconical portion 352 and which seats against the frustoconical seat 356and in so doing compresses the corner of a conformable seal ring to sealthe second bore 62 from the first bore 60.

To form or assemble the check valve assembly 304, conformable seal ring322 is located against conformable ring ledge 336, and backing ring 320is placed thereover to rest on backing ring ledge 334. Closure element308 is located in the cup shaped recess of the first body 312 such thatconical portion faces the annular openings of the backing ring 320 andconformable seal ring 322. The spring 318 is then placed in the cupshaped recess of the first body 312 of the closure element 308, and themale threaded portion 316 of the second body 314 is threaded into thethreads on the first body, thereby biasing the inner surface of thefirst annular portion 338 against the spring 318 and press the backingring against the backing ring ledge 334 to secure the conformable sealring 322 between the backing ring 320 and the conformable ring ledge336. The thus prepared check valve assembly is inserted into the firstbore 60 such that the conical portion 352 faces away from the secondbore 62. The inlet connector 18 is then secured over the base 26 of thevalve body 12 to secure the check valve assembly 304 in the first bore60.

In FIG. 10 , the check valve assembly 304 is shown in the closureelement 308 open position, which occurs when the force created by theinlet pressure from the monitored fluid line on the portion of theconical sealing surface 354 exposed within the inner circumference ofthe conformable seal ring 322 exceeds force of the spring 318 biasingthe conical sealing face against the inner circumferential surface ofthe conformable sealing ring 354, such as when an overpressure conditionis present in the monitored fluid line. Note, that where the closingpressure of the closure element 308 against surfaces of the conformableseal ring 354 during normal operating conditions is less than thatpressure required for the relief valve 10 to operate to relieve anoverpressure condition in the monitored fluid line to the vent, theclosure element 308 will commonly be seated against the seat 356 asshown in FIG. 11 unless an overpressure condition is present in themonitored fluid line connected to the inlet 170 of the relief valve 10.

Removable sealing plug 20 is received within the auxiliary pumping port28, and here is configured as a two-piece element, including a seal pin360 having a conical head portion 362 and a shaft portion 364 extendingfrom the conical head portion 362 with a retainer ledge 366 formedtherebetween, and a threaded insert 368 having an outer threaded wall370 and a central through bore 372 within which shaft portion 364 isreceived. Auxiliary pumping port includes a threaded first pumping portbore 374 extending inwardly of the outer surface of the valve body 12and a smaller second pumping bore 376 leading therefrom and into thesecond bore 62 of the valve body 12. The threaded insert 368 having theshaft portion 364 of the seal pin 360 therein, is threaded into thefirst pumping bore 374 to secure the conical head portion 362 of theshaft portion 360 in sealing engagement with a surface of the auxiliarypumping port. Here, a frustoconical annular ledge 378 extends betweenthe first and second pumping bores 374, 376, and the conical headportion 362 engages, and seals, against the frustoconical annular ledge378.

To determine the opening pressure of the valve, or the pressure at whichthe valve seal “cracks”, the pumping port plug 20 is removed byunthreading it from the auxiliary pumping port 28, and a threadedfitting 380 on the end of a tubing 382 extending from a fluid pump 384is threaded. The pump 384, here shown schematically as a manual pump butmay also be a non-manual pump, is used to pump fluid directly into thesecond bore 62 by pumping the fluid through the auxiliary pumping port28, to increase the pressure thereof, whereby the check valve closureelement 308 if not already seated on the seat 356, becomes seatedthereon, and fluid is pumped into the sealed volume of the second bore62 until the piston 66 begins moving against the bias of the spring 34to move the annular seal face 110 to the position thereof shown in FIG.6 , at which the pressurized fluid begins to vent from the second bore62 into the vent, which pressure is the cracking or opening set pressureof the relief valve 10. Thus, the opening pressure of the valve can bedetermined which the valve 10 is connected to other fluid components ina fluid circuit, such as a fluid control circuit, without adverselyaffecting the other components in the fluid circuit Additionally, thisprocedure can be repeated for different compression or spring forcesettings of the spring 34. As the force of the spring 34 against theupper surface of the spring plate is adjustable and is set by adjustingthe compression of the spring 34 by rotating the spring cap 14 withrespect to the body 12 of the valve 10, the procedure of determining thecracking pressure of the shear seal can be repeated for differentrotation positions of the spring cap 14 with respect to the body 12, andthereby the calibration of the rotatable setting of the spring cap 14 tothe cracking pressure of the relief valve 10 (or 200), or of the shearseal therein, can be reestablished while the relief valve isinterconnected to a fluid circuit, such as between a monitored fluidline and a vent. Because the check valve assembly 304 isolates the inlet170, and thus the monitored fluid line attached thereto, from the secondbore 62, the pressurizing of the second bore to determine the opening orcracking pressure of the shear seal or valve can be performed withouteffecting the components connected to the monitored fluid line.

What is claimed is:
 1. A pressure relief valve, comprising: a valve bodyincluding an inlet having an inlet pressure leading to an inner volumeof the valve, a piston having a shear seal bore extending therethrough,a first vent passage and a second vent passage and a T-shaped, incross-section, first seal plate adaptor having a seal plate surfacethereon and a passage therethrough in fluid communication with the firstvent passage and a first fluid pressure there present and a T-shaped, incross-section, second seal plate adaptor having a seal plate surfacethereon and a passage therethrough in fluid communication with thesecond vent passage and a second fluid pressure there present; a firstshear seal element locatable within the shear seal bore comprising; afirst seal surface having a first annular area facing the first sealplate adaptor; and an first annular shear seal element ledge having anannular surface area at least twice as large as the first annular area,the first annular shear seal element ledge facing away from the firstannular area; a second shear seal element locatable within the shearseal bore comprising: a second seal surface having a second annular areafacing the second seal plate adaptor; and a second annular shear sealelement ledge having an annular surface area at least twice as large asthe second annular area, the second annular shear seal element ledgefacing away from the second annular area, wherein the first annularshear seal element ledge face the second annular seal element ledge; abiasing seal ring in contact with the first annular shear seal elementledge and the second annular seal element ledge; wherein, the first sealplate adaptor has a first seal groove having therein a first seal ringand at least one first backing ring; and wherein, the second seal plateadaptor has a second seal groove having therein a second seal ring andat least one second backing ring.
 2. The pressure relief valve accordingto claim 1, wherein the first annular shear seal element ledge and thesecond annular seal element ledge are opposing surfaces of a seal gland,and the biasing seal ring contacts the first annular shear seal elementledge and the second annular seal element ledge.
 3. The pressure reliefvalve according to claim 2, wherein the biasing seal ring in a freestate, has a first width in the direction between the first annularshear seal element ledge and the second annular seal element ledge, andin the seal gland, the width of the biasing seal ring in the directionbetween the first annular shear seal element ledge and the secondannular seal element ledge contacting the biasing seal ring is less thanthe first width.
 4. The pressure relief valve according to claim 3,wherein the first shear seal element includes a through bore in fluidcommunication with a first vent bore and a second vent bore.
 5. Thepressure relief valve of claim 4, wherein a first space is presentbetween a portion of an outer surface of the biasing seal ring and thesecond annular seal element ledge, and the first space is maintained atthe pressure of the inner volume.
 6. The pressure relief valve of claim4, wherein a second space is present between a portion of an outersurface of the biasing seal ring and the first annular seal elementledge, and the second space is maintained at the pressure of the firstvent passage and the second vent passage.
 7. The pressure relief valveof claim 4, wherein a first space is present between a portion of anouter surface of the biasing seal ring and the second annular sealelement ledge, and the first space is maintained at a monitored inletpressure, and a second space is present between a portion of the outersurface of the biasing seal ring and the first annular seal elementledge.
 8. The pressure relief valve of claim 7, wherein the first shearseal element further comprises a major portion received within the shearseal bore and a minor portion extending inwardly of the second shearseal element, and the first annular seal element ledge extends betweenthe major portion and the minor portion.
 9. The pressure relief valve ofclaim 8, wherein the second shear seal element further comprises a firstinner bore and an outer circumferential surface, and the minor portionof the first shear seal element extends inwardly of the first inner boreand the second annular seal element ledge extends between the firstinner bore of the second shear seal element and the outercircumferential surface of the second shear seal element.
 10. Thepressure relief valve of claim 9, wherein a third space is presentbetween the minor portion of the first shear seal element and the firstinner bore of the second shear seal element, and the third space is influid communication with at least one of the first vent bore and thesecond vent bore.
 11. The pressure relief valve of claim 9, wherein afourth space is present between the outer circumferential surface of thesecond shear seal element and the shear seal bore, and the fourth spaceis in fluid communication with the inner volume of the valve.
 12. Thepressure relief valve of claim 9, further comprising a fifth space ispresent between the major portion of the first shear seal element andthe shear seal bore, and the fifth space is in fluid communication withthe inner volume of the valve.
 13. The pressure relief valve of claim10, in a first position the biasing seal element is spaced from theminor portion and in contact with the shear seal bore.
 14. The pressurerelief valve of claim 10, wherein in a second position the biasing sealring is spaced from the shear seal bore and in contact with the minorportion of the first shear seal element.
 15. The pressure relief valveof claim 1, wherein the piston further comprises a first recess having afirst recess wall, and the shear seal bore extends inwardly of the firstrecess wall.
 16. The pressure relief valve of claim 15, wherein thepiston further comprises a second recess having a second recess wall,and the shear seal bore extends inwardly of the second recess wall. 17.The pressure relief valve of claim 15, wherein the valve body furthercomprises a piston bore, and the first seal plate extends inwardly ofthe piston bore.
 18. The pressure relief valve of claim 17, wherein thepiston further includes a recess ledge, the recess ledge overlies atleast a portion of the first seal plate or the second seal plateextending inwardly of the piston bore.